Microwave beam width

I guess we all know laser beams. I wonder if we can make beams in the microwave frequency range and how the beam width relates to the frequency, e.g what is the minimum beam width we can achieve with a frequeny of 50Ghz.

I can see beam width is expressed in degrees of an angle and not in units of length. So beams have cone shape and not cylindrical shape afterall? Or (I believe thats the case) is it that they have no shape at all, we just "make up" their shape by considering cutoff values in the power of the field?

yes that's correct. Even a well colluminated laser beam will spread out over a distance
a radio signal even more so

a radio signal beamwidth is usually given ( as you saw) in degrees and to its -3dB ( half power) points either side of the beam centreline. Beamwidth is very dependant on frequency and antenna gain
My 24GHz signal from a 1 metre diameter dish has a -3dB beamwidth of about 4 degrees ( ~ 2 deg either side of the centreline)